In my previous article I talked about what makes a good wall and the different protective layers that need to be considered when designing one.
In this article, however, I will be presenting the wall as a constructions system. This is because more often than not, a great deal of consideration has to be put in how will you build your building. And there are many ways to look at a building, one of which is the construction system.
To get this out of the way, what is a construction system?
“A construction system is the combination of materials used to build the main load-bearing elements of a building — walls, floor, and roof.” — Back to Basics
Why is this important? Well a good construction system takes in account many factors depending on the uniqueness of the building. Back to Basics gives us a list of some of the most important aspects:
- Climate and geographic location
- Client’s needs and requirements
- Resources and available transportation
- Ease and speed of construction
- Maintenance requirements of materials
- Durability
- Thermal characteristics
- Energy consumption
- Environmental impact
- Cost-effectiveness
- Market perceptions and familiarity with the given product
- Recycling and reuse of the materials
There are several well known construction systems, some of which have been used for hundreds if not thousands of years. Over time, walls have been categorized in many ways, but in this article we will discuss them according to their mass.
First off, mass refers to the wall’s capacity to store heat. ASHRAE (The American Society of Heating, Refrigerating and Air-Conditioning Engineers) defines a mass wall as:
“Any concrete or masonry wall with a heat capacity exceeding 7 Btu/ft2●°F. If the mass elements are constructed with lightweight materials with a unit weight not greater than 120 lbs/ft3 then the HC must be greater than 5 Btu/ft2●°F in order to qualify as a mass wall.” — Building Enclosure
But for the sake of keeping things simple, we will be looking at walls as high mass walls (or heavyweight) and lightweight walls.
High mass walls
Are walls that provide energy efficiency through their mass and have high heat capacity levels. They are typically heavyweight walls made out of concrete blocks, concrete, insulated concrete forms, masonry cavity, brick other than brick veneer, earth and solid timber or logs. (source)
Pros:
- The main characteristic of high mass walls is their capacity to store heat.
- This is great in areas where there are high fluctuations of temperature between day and night which lead to better thermal comfort.
- They are also low maintenance, can reduce operational energy use and have a relative long lifespan.
Cons:
- Unfortunately most materials used for such walls have a high embodied energy. This means that they use a lot of energy in production (including assembly, maintenance, and recycling/demotion).
Lightweight walls
Compared to the high mass walls, these walls do not have a high heat capacity, but they are required to have high insulation value. Most lightweight walls are made out of timber or steel frames structures, structural insulated panels, prefabricated products, fiber cement, polystyrene building products, etc.
Pros:
- They respond faster to temperature changes, so it is preferred in warm climates.
- They are also easier to transport over longer distances, meaning that they are more accessible to remote sites.
- They also have a lower embodied energy and impact on production.
- The lightweight walls allow a large range of cladding options if there is a drainage cavity between the framing and the cladding.
Cons:
- Unlike the high mass walls, these wall have a shorter lifespan and
- Require higher operational energy such as heating or cooling.
- This also means that they a higher maintenance need.
Of course there is no perfect solution, rather than a list of options that are carefully chosen for your unique situation (this applies to all of the building’s elements).
The good thing is that you can easily research and be informed about each construction system as technologies improve and the demand for more sustainable or high performing buildings increases.
In part 2, I will go through the different materials used in buildings and their characteristics.
